title: Group B Streptococcus serotypes III and V induce apoptosis and necrosis of human epithelial A549 cells.
abstract: Although group B Streptococcus (GBS) has been classically described as an exclusively extracellular pathogen, growing evidence suggests that it may be internalized by epithelial cells. However, the fates of intracellular GBS and of infected respiratory epithelial cells remain unclear. Little is known about the bacterial components involved in these processes. The present study investigated the bacterial internalization by A549 cells and the apoptosis/necrosis of the infected human epithelial cells. The morphological changes in A549 cells observed from 2 h post-infection with GBS included vacuolization and the formation of apoptotic bodies. Flow cytometry revealed that 81.2% of apoptotic A549 cells were infected with GBS serotype III 90356-liquor. Moreover, a double-staining assay using propidium iodide (PI)/Annexin V (AV) gave information about the numbers of viable (PI-/AV-) (18.27%) vs. early apoptotic (PI-/AV+) (73.83%) and late apoptotic cells (PI+/AV+) (7.37%) during infection of A549 cells with GBS III 90356-liquor. In addition, 37% necrotic cells were observed in A549 cells infected with GBS serotype V 90186-blood. In conclusion, GBS serotypes III and V induce apoptosis of epithelial cells in the early stages of GBS infection, resulting in tissue destruction, bacterial spreading and, in consequence, invasive disease or systemic infection.
authors.affiliation: Departamento de Biologia Celular, Instituto de Biologia Roberto Alcântara Gomes, Universidade do Estado do Rio de Janeiro, Brazil.
authors.forename: Andréia Ferreira Eduardo
authors.initials: AF
authors.lastname: Da Costa
authors.forename: Camila Serva
authors.initials: CS
authors.lastname: Pereira
authors.forename: Gabriela Da Silva
authors.initials: Gda S
authors.lastname: Santos
authors.forename: Técia Maria Ulisses
authors.initials: TM
authors.lastname: Carvalho
authors.forename: Raphael
authors.initials: R
authors.lastname: Hirata
authors.forename: Ana Luiza
authors.initials: AL
authors.lastname: De Mattos-Guaraldi
authors.forename: Ana Cláudia De Paula
authors.initials: AC
authors.lastname: Rosa
authors.forename: Prescilla Emy
authors.initials: PE
authors.lastname: Nagao
mesh_terms: D017209:Apoptosis; D001422:Bacterial Adhesion; D045744:Cell Line, Tumor; D002470:Cell Survival; D015169:Colony Count, Microbial; D057899:Cytophagocytosis; D004847:Epithelial Cells / Q000382:microbiology* / Q000473:pathology / Q000648:ultrastructure; D006801:Humans; D009336:Necrosis; D012703:Serotyping; D013292:Streptococcus agalactiae / Q000502:physiology*